Field
Embodiments of the present disclosure generally relate to an apparatus for processing large area substrates. More particularly, embodiments of the present disclosure relate to an atomic layer deposition (ALD) system for device fabrication and in situ cleaning methods for a showerhead of the same.
Description of the Related Art
Organic light emitting diodes (OLED) are used in the manufacture of television screens, computer monitors, mobile phones, other hand-held devices, etc. for displaying information. A typical OLED may include layers of organic material situated between two electrodes that are all deposited on a substrate in a manner to form a matrix display panel having pixels that may be individually energized. The OLED is generally placed between two glass panels, and the edges of the glass panels are sealed to encapsulate the OLED therein.
The OLED industry, as well as other industries that utilize substrate processing techniques, encapsulate moisture-sensitive devices to protect them from ambient moisture exposure. A thin conformal layer of material has been proposed as a means of reducing Water Vapor Transmission Rate (WVTR) through encapsulation layer(s). Currently, there are a number of commercial ways to encapsulate devices. Using an ALD process to cover a moisture-sensitive device is being considered to determine if the conformal nature of these coatings can provide a more effective moisture barrier than other coatings.
ALD is based upon atomic layer epitaxy (ALE) and employs chemisorption techniques to deliver precursor molecules on a substrate surface in sequential cycles. The cycle exposes the substrate surface to a first precursor and then to a second precursor. Optionally, a purge gas may be introduced between introductions of the precursors. The first and second precursors react to form a product compound as a film on the substrate surface. The cycle is repeated to form the layer to a desired thickness.
One method of performing ALD is by Time-Separated (TS) pulses of precursor gases. TS-ALD has several advantages over other methods, however one drawback of TS-ALD is that every surface (e.g., the interior of the chamber) exposed to the precursors will be coated with deposition. If these deposits are not removed periodically, the deposits will tend to flake and peel off eventually, leading to particulates ending up on the substrate and hence degraded moisture barrier performance of the deposited layer. If there is no effective way to clean the undesired deposits from the chamber surfaces in situ, then those chamber surfaces must be removed for cleaning “off-line”. If the chamber has to be opened to accomplish removing and replacing chamber surfaces for cleaning, then vacuum has to be broken in the chamber (e.g., the chamber is brought to atmospheric pressure) and this breaking of vacuum will lead to excessive chamber down-time.
There is a need, therefore, for a processing chamber allowing for removal and cleaning of the main key elements of the chamber which will accumulate extraneous deposits with minimal down-time.